Here's an easier question for you: how many tens are there in ten million? Answer: one million. The reason is that you divide the two numbers. ten million divided by ten is one million. If you write it in fraction form, this is

10 000 000
---------------
10

and you can cross off a zero on the top and a zero on the bottom. This leaves just a 1 on the bottom and 10 000 00 (or 1 million) on the top. Anything divided by 1 is just the original number, so the answer is 1 million. If you have 100 on the bottom (what is ten million divided by 100?) then you can cross off two zeros on the bottom and two zeros on the top. That gives you 10 000 0 over 1, which is one hundred thousand.